Vacuum-regulator for x-ray tubes.



B.EBAKER., VACUUM REGULATOR FOR X-RAY TUBES.

APPLICATION FILED JUNEQ. 1911. 7

1,027,795. Patented May 28, 1912.

wn'ncsscs- Y HWEHTOR ATTORNEY UNITED STATES PATENT OFFICE.

BURTON E. BAKER, or HARTFORD, CONNECTICUT.

VACUUM-REGULATOR FOR X-RAY TUBES.

To all whom it may concern:

Be it known that I, BURTON E. BAKER, a citizen of the United States,residing at Hartford, in the county of Hartford and State ofConnecticut, have invented a new and useful Vacuum-Regulator for X-RayTubes, of which the following is a specification.

My invention relates to an improved regulator. for Roentgen or X-raytubes.

The objects of my invention are, first, to provide a regulator whichwill operate only when the user of the tube desires to change theintensity of the vacuum therein; second, to allow the user to controlreadily the extent of regulation as he may desire; third, to provide aregulator which is simple in operation and which will last.

Further objects and advantages of my in- *vention will be set forth inthe detailed description below. I

It is well known that the rarity of 'the vacuum in an X-ray tube Variesfrom time to time as the tube is used and that the tendency of thevacuum under use is to become more and more rarefied so that it becomesdifiicult for the electric current to pass through the tube which thusbecomes unsteady and will not produce uniform re sults. Frequently thevacuum becomes so rarefied that it is impossible to pass current throughthe tube at all. At an early stage in the development of the art it wasfound that this trouble might be remedied by introducing gas into thetube when the vacuum be.- came too rarefied to permit normal operation.For that purpose a small glass cell was sealed into the tube proper andinto this cell was packed asbestos fiber saturated with potassiumhydrate, sodium formate',"oi other suitable material which would throwoff gas when heated. To reduce the vacuum, the operator applied heat tothis glass cell and its contents by means of a flame. This method isobjectionable because it is dirty i and awkward to apply, because itsometimes cracks the glass, and because it is difiicult to measure theamount of regulation obtained. At a later period in the history of theart, regulation was effected by running a wire through this glass celland its inclosed gas producing mixture. The latter is heated by passingan electric current through this wire. Some tube makers have attemptedSpecification of Letters Patent.

Application filed June 9, 1911.

Serial No. 632,283.

. automatic regulation by connecting this wire to the main electrlccircuit by a shunt circuit with a spark gap of such resistance that thecurrent will pass across itand heat the regulating mixture when theresistance of the vacuum in the tube becomes greater than the resistanceof the spark gap. A serious objection to this mode of regulation is thatwhen the current has once started through the shunt circuit it tends topersist cian comparatively inexpert in electrical matters, to properlyadjust his spark gap.

Patented May 28,1912. 7

and thereby causes over-regulation. And it 'is diflicult for theoperator, usually a physibestos, forming a path which the currentfollows, soiling the tube by throwingcanbonized particles into it, andnot readily heating the gas producing mixture. This does not occur withmy regulator because less heat is used and the asbestos does not becomecarbonized.

In the accompanying drawings, Figure 1 is a cross-sectional View of anX-ray tube containing my regulator. Fig. 2 is a perspective view of thesame.

Like numerals designate similar parts throughout the several views.

In the accompanying drawings, 4 is a Roentgen or X-ray tube of the usualtype. 5 and 6 are the main discharge terminals of said tube, 5 being thecathode and 6 the anode in the usual operation of the tube.

7 is a wire sealed into the tube, electrically connected with thecathode 5,and extending outside the tube to be connected with the sourceof electric current. 8 is a similar wire connecting the "anode 6 withthe source of electric current.

9 is a small cathode or metaldisk with its surface preferably concaved,attached to the anode 6 at or near the point shown in the drawings byscrewing it into the anode or by other suitable means.

10 is a glass cell open at its. inner end and sealed into the'glass ofthe tube proper at.

the point 11. In the cell 10 there are a number of orifices 12 insidethe main tube.

13 is a mass-of asbestos fiber or other suitable material saturatedwitha volatile salt IOU or other chemical which will produce gas whenheated. The" shoulder 14.- prevents the mixture 13 from passing into themain tube. is a small metal disk resting against the shoulder 1 1; i v

The operation of my device is as follows: When the tube is used for theproduction of Xrays in the ordinary way, the wire 7 is connected withthe negative pole .of the electric coil or other source of current andthe wire 8 with the positive pole. As the cathode stream runs only fromthe negative pole toward the positive, there is no cathode stream fromthe small cathode 9 and no .8. Usually, however, the operator uses anelectric coil or other device provided with a switch which enables himto run the current in either. direction twill. When the current isreversed and the discharge term1nal 6 becomes the negative pole of thetube, a cathode streamds discharged from the small cathode 9. As theopen end of the cell 10 is placed within the focalfield of the cathode9, this cathode stream impinges upon the disk 15, heating the disk 15and the gas producing mixture 13 behind it. The gas thus produced passesthrough the orifices 12 into the tube proper and thus reduces the rarityof the vacuum. It has been found in practice that a momentary reversalof the current will usually eliect sufficient regulation. a

The disk may be omitted and the cathode stream from the small cathode 9allowed to strike directly into the gas producing mixture 13. Goodpractical results may be obtained in. this manner. When this r is done,the orifices 12 may be omitted if preferred.

While the parts shown and described are well adapted to serve thepurposes set forth, it is to he understood that my invention is notlimited thereto, for changes may be made in the details of my devicewithout departure therefrom.

Having described my invention, what I claim is:

1. In an X-ray tube, the combination of electric discharge terminalshoused therein and operative under normal conditions of current flow asan anode and a cathode respectively, a producing medium housed withinsaid tube, and means for concentrating cathode rays on said'medium uponthe reversal of the direction of said current flow.

2. In X-ray tube, the combination of.

current flow as an anode and a cathode respectively, an auxiliarydischarge terminal electrically connected with said terminal normallyoperative asan anode, a cell in the focal field of said auxiliaryterminal, a gas producing element within said cell, and means forcausing the reversal of the direction of said current flow.

4. In an X-ray tube, the combination of a principal cathode and aprincipal anode, an auxiliary cathode mounted upon said principal anode,a cell in the focal field of said auxiliary cathode, and a gas producingelement within said cell.

5. In' an X-ray tube, the combination of a principal cathode and aprincipal anode,

an auxiliary cathode mounted upon said principal anode, a cell in thefocal field of said auxiliary cathode, a gas producing element withinsaid cell, and means for causing an electric current tofiow through saidtube in either direction.

6. In an X-ray tube, the combination of a principal cathode and aprincipal anode,

an auxiliary cathode electrically connected with said principal anode, acell in the focal field of said auxiliary cathode, and a gas producingelement within said cell.

7 In an X-ray tube, the combination of a principal cathode and aprincipal anode, an auxiliary cathode electrically connected with saidprincipal anode, a cell in the focal field of said auxiliary cathode, agas producing element within said cell, and means for causing anelectric current to flow through said tube in oitherdirection.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

BURTON BAKER. lVitnesses KATE F. VVoLrn, GRACE E. GLiN'rsMAN.

tic-pies off this patent may be obtained for five cents each, byaddressing the Commissioner of Patents,

Washington, 110.

